.bk-logo {
  margin: 5px;
  position: relative;
  display: block;
  background-repeat: no-repeat;
  &.bk-grey {
    filter: url("data:image/svg+xml;utf8,<svg xmlns=\'http://www.w3.org/2000/svg\'><filter id=\'grayscale\'><feColorMatrix type=\'matrix\' values=\'0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0 0 0 1 0\'/></filter></svg>#grayscale"); /* Firefox 10+, Firefox on Android */
    filter: gray; /* IE6-9 */
    -webkit-filter: grayscale(100%); /* Chrome 19+, Safari 6+, Safari 6+ iOS */
  }
}

.bk-logo-notebook {
  display: inline-block;
  vertical-align: middle;
  margin-right: 5px;
}

.bk-logo-small {
  width: 20px;
  height: 20px;
  background-image: url();
}

.bk-logo-medium {
  width: 35px;
  height: 35px;
  background-image: url();
}

.bk-logo-large {
  width: 75px;
  height: 75px;
  background-image: url();
}
